Catalyst composition for the preparation of ethylene from ethane

ABSTRACT

Solid solution catalyst in particulate form consisting of attrition resistant  alpha -Al2O3 particles with 0.5 to 10% by weight, expressed as the oxide, of iron cations substituted for aluminum cations in said catalyst support stabilized with 0.5 to 10% by weight, expressed as the oxide, of lanthanum and modified with at least two, preferably three, metal cations selected from the metals consisting of chromium, cobalt, magnesium, manganese, and barium; wherein one of said metal cations is barium and said catalyst has X-ray diffraction pattern with peak positions different than that of the  alpha -Al2O3 structure. A process is disclosed which produces ethylene from ethane while producing reduced amounts of vinyl chloride from said ethane to ethylene process.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of copending U.S. patentapplication Ser. No. 07/567,510 filed Aug. 15, 1990, now abandoned.

FIELD OF THE INVENTION

This invention relates to a catalyst for converting ethane to ethylenewhereby the amount of vinyl chloride formed in the reaction is reduced.A process is disclosed which converts ethane to ethylene and theethylene containing stream is subsequently fed to an oxychlorinationprocess to convert the ethylene to ethylene dichloride.

BACKGROUND OF THE INVENTION

Vinyl chloride can be prepared using a number of well known processes.Two familiar processes are the hydrochlorination of acetylene and theoxychlorination of ethylene to form dichloroethane which in turn isdehydrohalogenated to form vinyl chloride, see U.S. Pat. No. 2,847,483.As acetylene is more expensive than ethylene, the latter process iseconomically favored and much activity is noted in this art area, seeU.S. Pat. No's. 3,634,330; 3,454,663; 3,448,057; and 3,624,170.Ethylene, in turn, can be prepared by the oxydehydrogenation of ethane,see U.S. Pat. No. 3,769,362. In all processes, high yields of ethyleneare particularly desired. In processes which use ethane as a feed stockin the presence of either chlorine or hydrogen chloride, they canproduce not only ethylene but also can directly produce vinyl chlorideand other valuable products such as ethylene dichloride, ethyl chloride,and the like. The ethylene, ethylene dichloride, and ethyl chloride canbe readily reacted to form more vinyl chloride.

Preparation of vinyl chloride can be effected by the balanced vinylchloride monomer (VCM) process, as described in the article entitled"Oxychlorination of Ethylene" by Messrs. Cowfer and Magistro in"Encyclopedia of Chem. Tech., 3rd Ed; Wiley; New York, 1983; Vol. 23,pp. 865-885. The balanced vinyl chloride monomer process isschematically illustrated in FIG. 1, herein.

In one proposed method in which ethylene is produced, ethane, a chlorinesource and oxygen are passed through a reactor maintained at about 550°C. where fluidized solid solution catalyst is used to produce a streamfrom the reactor containing ethylene, hydrogen chloride, vinyl chlorideand water. The amount of vinyl chloride in this stream, also identifiedas Stream A in the drawings, was in the range of 7-25% on molarefficiency basis; that is, 7-25 moles of vinyl chloride were producedfor every 100 moles of ethane which were fed to the reactor. Stream Awas fed into a separator where vinyl chloride was separated fromethylene and other constituents. Ethylene and other constituents werefed into the oxychlorination unit of FIG. 1 and the ethylene dichlorideproduct was treated and subsequently produced vinyl chloride monomer, asoutlined in FIG. 1.

A proposed process of using a separator to separate vinyl chloride fromethylene and other constituents is schematically depicted in FIG. 2. Itwould be desirable to produce ethylene from ethane whereby the amount ofvinyl chloride produced would be minimized so as to reduce or eliminatethe separation step thus allowing the product stream containing ethyleneto be fed directly to an oxychlorination process unit.

SUMMARY OF THE INVENTION

This invention is directed to a solid solution catalyst which is used toconvert ethane, a chlorine source such as hydrogen chloride, and oxygento a stream containing ethylene, hydrogen chloride, vinyl chloride,carbon oxides, chlorinated by-products, and water wherein the objectiveis to minimize the amount of vinyl chloride and which stream does nothave vinyl chloride removed but is passed directly into theoxychlorination unit and the ethylene dichloride product is treated andsubsequently produces vinyl chloride. The catalyst comprises ironcations substituted for aluminum cations in a host lattice of attritionresistant α-Al₂ 0₃ particles having an iron content of 0.1 to 20% byweight expressed as the oxide stabilized with a total lanthanide contentof 0.1 to 20% by weight expressed as the oxide and modified with atleast two, preferably more than two, metal cations selected from themetals consisting of cobalt, manganese, chromium, magnesium and barium,wherein barium must be present as one of the metal cations. Amount ofeach of the metals is 0.05 to 10%, preferably 0.1 to 3%, and morepreferably 0.2 to 2% by weight, based on the weight of the catalyst,including the alumina.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of the balanced vinyl chloride monomer processwhere ethylene and chlorine are ultimately converted to vinyl chloridemonomer;

FIG. 2 is a flow diagram of a process for reacting ethane, a chlorinesource such as hydrogen chloride and oxygen to produce a stream, streamA, containing ethylene, hydrogen chloride, vinyl chloride and watervapor, passing the stream to a separator in order to separate vinylchloride from a stream containing ethylene and hydrogen chloride;passing the stream containing ethylene and hydrogen chloride to theoxychlorination unit to produce ethylene dichloride and passing theethylene dichloride to a pyrolysis unit to produce vinyl chloride andpassing vinyl chloride to a vinyl chloride purification unit of thebalanced vinyl chloride monomer process; and

FIG. 3 is a process similar to the one depicted in FIG. 2 except thatthe resulting stream, stream B, from the reaction of ethane, a chlorinesource and oxygen is conveyed directly to the oxychlorination unit ofthe balanced vinyl chloride monomer process without a separation ofvinyl chloride.

DETAILED DESCRIPTION OF THE INVENTION

U.S. Pat. No. 4,158,645 describes a fluidized solid solution catalystbased on alpha alumina containing iron stabilized with lanthanum and/orlanthanides and modified with metal cations selected from lithium,cobalt, copper, magnesium, chromium, and manganese in amount of 0.1 to5% by weight expressed as oxide. Such catalysts have improvedselectivity for the formation of vinyl chloride and/or have increasedcatalyst life.

The catalysts described in the previous paragraph promote the reactionof ethane with hydrogen chloride and oxygen at about 550° C. to producea gaseous stream, also referred to herein as Stream A, of ethylene,hydrogen chloride, vinyl chloride monomer, and water vapor. Amount ofvinyl chloride in this stream or Stream A is in the range of 7 to 25mole percent. This stream is then taken to a separator where vinylchloride is separated from ethylene and hydrogen chloride. The separatedvinyl chloride is then taken to the vinyl chloride purification unitshown in FIG. 1 where it is purified into vinyl chloride product. Theseparated ethylene and hydrogen chloride from the separator are taken tothe oxychlorination unit of FIG. 1 where ethylene dichloride is producedin accordance with the following equation: ##STR1##

For the proposed new catalyst and process of this invention with noseparation (FIG. 3) described in this patent, it is desired to minimizevinyl chloride in Stream B because unwanted ethylene trichloride(1,1,2-trichloroethane) is produced from vinyl chloride in theoxychlorination according to the following equation: ##STR2## Thetrichloroethane by-product is undesirable and is combined with otherchlorinated hydrocarbon by-products (light and heavy ends) for disposal.The above equation shows why it is desirable to minimize the amount ofvinyl chloride in Stream B so that the amount of the trichloroethaneby-product is correspondingly reduced. Disposal costs, and processeconomics, are strongly dependent on the amount of trichloroethane(1,1,2-trichloroethane) that is formed. Since the presence oftrichloroethane is dependent on the presence of vinyl chloride in StreamB, it is desired to minimize the amount of vinyl chloride in Stream Bthus reducing costs of the vinyl chloride process due to the reduceddisposal costs.

The catalyst of this invention is effective in reducing the amount ofvinyl chloride in Stream B to a level of less than about 5% yield onmolar basis, preferably below 4%, more preferably below 3%, andespecially below 2%. By reducing the amount of vinyl chloride, Stream Bcan be taken directly to the oxychlorination unit shown in FIG. 1 thusby-passing and doing away with the separator shown in FIG. 2. Reducedvinyl chloride formation in the ethane t ethylene process will causeless by-products from vinyl chloride monomer to be produced, therefore,reducing the cost of disposal. This will reduce process costs fordisposal of unwanted by products from the oxychlorination process. Thisreduced vinyl chloride monomer allows the elimination of the need for aseparator and, therefore, further lowers the overall process costs.

The catalyst of this invention is a solid solution catalyst based onalpha alumina containing iron stabilized with lanthanum and/orlanthanides and modified with at least two of select metals, preferablymore than two of select metals. The solid solution catalysts of thisinvention can contain 0.1 to 20%, preferably 0.5 to 10%, by weight, ofiron in the catalyst, expressed as iron oxide. The catalyst can containsimilar levels of lanthanum and/or lanthanide, expressed as the oxide.The select metals include cobalt, manganese, chromium, magnesium, andbarium, wherein barium must be present as one of the metals. The mostpreferred catalysts of this invention contain barium, cobalt, manganese,and chromium. The select metals are in the form of oxides or oxideprecursors such as nitrates. Amount of each select metal in thecatalyst, on oxide basis, is 0.05 to 10%, preferably 0.1 to 3%, and morepreferably 0.2 to 2%, on weight basis of the catalyst, including theweight of the alumina catalyst support. Preferred catalysts of thisinvention are the following catalysts identified as (1), (2), (3) and(4):

(1) 4% La₂ 0₃, 2% Fe₂ 0₃, 0.5% Cr₂ 0₃, 0.5% CoO, 1.5% BaO;

(1) 4% La₂ 0₃, 2% Fe₂ 0₃, 0.5% Cr₂ 0₃, 0.5% CoO, 1.5% BaO, 1.0% MnO;

(1) 4% La₂ 0₃, 2% Fe₂ 0₃, 0.5% Cr₂ 0₃, 0.5% CoO, 1.5% BaO, 2.0% MnO.

(1) 4% La₂ 0₃, 2% Fe₂ 0₃, 0.5% CoO, 1% MnO, 1.5% BaO.

In the above catalysts, 4% La₂ 0₃ indicates weight percent of lanthanumoxide in the final catalyst which includes the weight of the aluminacatalyst support. This applies to the other components in the catalystdisclosed in the disclosure herein, including the claims appendedhereto.

In carrying out the reaction between ethane, a chlorine source, andoxygen using the catalyst of this invention, ethane is reacted withoxygen and the chlorine source in the presence of the solid solutionparticulate catalyst of this invention containing iron which isstabilized with lanthanum and/or lanthanides and modified with at leasttwo selected metal cations, one of which must be barium, to prepare astream, stream B, containing ethylene, vinyl chloride, hydrogenchloride, and water vapor. If vinyl chloride enters the oxychlorinationunit, it is readily converted to 1,1,2-trichloroethane and thisby-product component reduces the yield of desirable products andincreases the by-product disposal capacity requirements. It is,therefore, desired to reduce production of vinyl chloride at this stageto below about 5% yield on molar basis, preferably below 4%, andespecially below about 2%. When the vinyl chloride is reduced to theabove level, it allows the removal of the separator and often results ina significant reduction in process cost. Depending upon feed and reactorconditions, conversion of ethane to products is 90 to 95% by mole, yieldof ethylene is 85 to 90% by mole, and yield of the sum of ethylene andvinyl chloride is 85 to 90% on molar basis.

In the process, ethane, oxygen and a chlorine source are placed into areactor vessel containing a solid solution catalyst of this invention.The process contemplates the use of standard techniques concerning thetype of operation, reactor size and design, and the like. The process isconducted as a continuous process wherein reactants and products arecontinuously added and withdrawn. The solid solution catalyst can befixed in a bed, it can be supported, or it can be present as particlesthat can readily fluidize during operation. A preferred embodiment ofthe process is to employ the solid solution catalyst in particulate formthat will fluidize in the process thereby establishing maximum contactwith the reactants. Such processes are known as fluid bed processes andthe reactors designed for such are known as fluid bed reactors. Atypical reactor is designed such that one or more gaseous reactants isintroduced in the reactor below the catalyst bed and the gas pressurizedthrough a support grid and suspends the catalyst in the reactor volume.Other reactants can be added at appropriate levels above, below, or anypoint in the fluid catalyst bed. Normally, products are withdrawn fromthe top portion of the reactor and collected or further treated asdesired.

Although the process contemplates the use of known operating techniquesand reaction conditions, certain conditions are herein stated as usefuland practical. The reactants comprise ethane, oxygen, usually used inthe form of air, and a chlorine source. The chlorine source ispreferably hydrogen chloride gas. Using one mole of ethane as a basis,the hydrogen chloride is used at from about 0.1 mole to about 10 molesor more. More preferably, the hydrogen chloride is used at a level offrom about 0.5 mole to 5 moles per mole of ethane. In general, as ahigher ratio of hydrogen chloride to ethane is used, the yield of vinylchloride and other chlorinated products increases and the yield ofethylene decreases. However, levels of use of hydrogen chloride above 5moles per mole of ethane also increase the amount of hydrogen chlorideto recycle. Excellent results have been obtained using about 1 to about4 moles of hydrogen chloride per mole of ethane. As both ethylene andvinyl chloride can be prepared in significant amounts using thecatalysts and as the yield of ethylene to vinyl chloride is highlydependent upon the hydrogen chloride to ethane ratio in the reactantfeed, the process can be termed either an oxydehydrogenation process toprepare ethylene or an oxychlorination and pyrolysis process to preparevinyl chloride.

Oxygen, preferably in the form of dry air, is used at from about 0.1mole to about 1.5 moles of oxygen to one mole of ethane. A morepreferred level is from about 0.5 mole to about 1 mole. The use oflevels of oxygen of about 1 mole per mole of ethane is preferred in anoxychlorination process. In an oxydehydrogenation process, excellentresults have been obtained using a level of oxygen of about 0.5 to 0.6mole per mole of ethane.

Ethane, oxygen, and hydrogen chloride are passed into the reactor asreactants. Temperature of the reaction ranges from 400° C. to 650° C.,and more preferably from 475° C. to 600° C. Materials withdrawn from thereactor in the product stream comprise ethylene, vinyl chloride,chlorinated products such as ethylene dichloride and ethyl chloride,carbon oxides (CO and CO₂), water, unreacted ethane and hydrogenchloride.

The improved feature in the oxydehydrogenation process described hereinis the use of a solid solution catalyst containing iron cationssubstituted for cations in the host alumina lattice which catalyst isstabilized with lanthanum and/or lanthanides and modified with at leasttwo selected metal cations, one of which must be barium. See U.S. Pat.No. 4,158,645 for a disclosure of a similar catalyst without barium. Thecatalyst is basically a solid solution of iron cations in a host aluminalattice. This is in contrast to catalysts wherein an active ingredientsuch as cupric chloride or iron oxide is merely adsorbed onto thesurface of a support structure or material. The difference is crucialand can be distinguished in the physical state of the catalyst, in theactivity of the catalyst, and in the life of the catalyst.

The solid solution catalyst is a true solution wherein iron cations aresubstituted for host lattice ions in the catalyst structure. An X-raydiffraction pattern of a solid solution catalyst is characteristic ofthe diffraction pattern of the host lattice. For example, a solidsolution catalyst of Fe₂ 0₃ in α-Al₂ 0₃.

A distinguishing feature of the solid solution catalysts of thisinvention, i.e., solid solution catalysts containing iron and stabilizedwith lanthanum and/or lanthanides and modified with at least two selectmetal cations, one of which must be barium, is in the increasedselectivity and/or retention of iron by the catalyst upon use andreduction of vinyl chloride in Stream B. For example, an α-Al₂ 0₃ solidsolution catalyst containing iron cations which is stabilized withlanthanum cations and modified with at least two metals, one of whichmust be barium, preferably at least three metals, one of which must bebarium, used at reaction conditions of 1 mole ethane/0.6 mole oxygen/1.5mole hydrogen chloride, lost about 0.2% by weight of its original ironcontent after over 100 hours of use. In contrast, a catalyst which is asolid solution of iron in α-Al₂ 0₃ stabilized with lanthanum but notmodified lost about 3% of its original iron content after about 100hours of use at the same set of conditions. In further contrast, acatalyst consisting of a simple solid solution of iron in α-Al₂ 0₃ lostabout 4% by weight of its iron content under the same conditions. In yetfurther contrast, a catalyst comprised of ferric oxide merely absorbedonto Al₂ 0₃, operating under the same set of conditions, lost over 8% byweight of its original iron content after about 100 hours of use.

The catalysts of this invention can also be prepared from attritionresistant catalyst supports. See U.S. Pat. No. 5,008,225 issued Apr. 16,1991, for description of the attrition resistant catalyst supports. Theattrition resistant catalyst support, when viewed under the electronmicroscope at 1000 × magnification, readily shows that the alpha-aluminaof the attrition resistant catalyst support mainly consists ofnon-aggregated or non-agglomerated particles that are substantially freeof crystalline boundaries. Since the particles are devoid of crystallinegrain boundaries, they are resistant to attrition. Aluminas of theattrition resistant alpha-alumina supports contain no surfacecrystalline grain boundaries. In order to have a low attritionalpha-alumina catalyst support, the final support should besubstantially devoid of any crystalline grain boundaries, fractures orcracks and should not consist of an aggregation or agglomeration of theparticles. The attrition resistant catalyst support is prepared in thesame way as the alumina catalyst support but has lower attrition due toformation of a surface with no crystalline grain boundaries duringprocessing.

Attrition resistance also depends on the physical form of the particles.Spheroidal particles with smooth surfaces will have lower attritionlosses than particles with irregular shapes and rough edges. The termspheroidal also is meant to include spherical, elliptical, oblong,globular, and the like, so long as there are no irregular or sharp edgesthat are prone to attrition during handling or fluidization. Theattrition resistant catalyst support is an inert substrate ofalpha-alumina wherein the alpha-alumina particles are devoid orsubstantially devoid of any fractures, cracks or crystalline grainboundaries and have attrition number not exceeding 30, preferably notexceeding 15, more preferably not exceeding 10, especially not exceeding5, and is thermally stable up to about 1000° C. The attrition number isdescribed in U.S. Pat. No. 5,008,225.

Solid solution catalysts containing iron cations can be of differenttypes. The iron exists as ferric (Fe⁺³) ions. The ferric ion is theactive ion in the catalyst. However, since ferrous ion can oxidize to aferric ion in the process, the use of solid solution catalystscontaining ferrous ions is within the scope of this invention.

In the solid solution catalyst containing iron cations there is directsubstitution of iron ions for host lattice ions. An example of thiscatalyst is (Fe_(x) ⁺³ M_(2-x) ⁺³)O₃ wherein x is greater than 0 andless than 2 and M is a metal such as aluminum or chromium. An example ofthis is a solid solution catalyst of ferric oxide (Fe₂ 0₃) in aluminumoxide (Al₂ 0₃). As the ferric ion is much greater in size than analuminum ⁺³ ion, the solubility of the ferric ion in aluminum oxide islimited. Hence, the solid solution catalysts of the example wherein M isaluminum encompass materials of the formula wherein x has an upper limitof about 0.15.

The solid solution catalyst containing iron is stabilized with lanthanumand/or a lanthanide. Although the lanthanum or lanthanide is an integralpart of the catalyst, it is believed that the lanthanum or lanthanidedoes not enter into solid solution with the host lattice as does theiron. Characterization of the catalysts of this invention will bediscussed further in a subsequent section of this specification.

The lanthanum and lanthanides can be employed in the solid solutioncatalysts singly or as mixtures of the metals. The lanthanides areelements 57 to 71 of the Periodic Table. More preferably, thelanthanides used are lanthanum, cerium, praseodymium, neodymium, andcatalyst of Fe₂ 0₃ in α-Al₂ 0₃ stabilized with lanthanum.

The solid solution catalyst containing iron and stabilized withlanthanum or a lanthanide is further modified with at least two selectmetal cations, one of which must be barium. The use of these cationsresults in a catalyst which reduces the amount of vinyl chloride in theproduct stream from the reaction of ethane, oxygen and a chlorine sourceand/or increased catalyst lifetime. The metal cations employed areselected from the group consisting of barium, chromium, manganese,magnesium, and cobalt, wherein barium must be present.

Although the selected metal cations are an integral part of thecatalyst, it is believed that the selected metals do not enter intosolid solution with the host lattice as does the iron.

The solid solution catalysts of this invention contain iron and haveX-ray diffraction patterns characteristic of the host lattice material.The catalyst is first identified and characterized by analyzing it todetermine what elements it contains. This can be done using well knowntechniques such as chemical analysis, atomic absorption spectroscopy,X-ray fluorescence spectroscopy, and optical microscopy. For example,the solid solution catalyst of iron oxide in aluminum oxide, stabilizedwith lanthanum and modified with cobalt and barium, would show iron,lanthanum, aluminum, cobalt, barium, and oxygen to be present in thecatalyst. The presence and quantity of iron in the catalyst can bereadily determined using a standard method of chemical analysis such asthe dichromate method for the determination of iron. The amount of ironin the solid solution catalysts is limited by the solubility of the ionsin the host lattice. Presence of alumina, cobalt, manganese, magnesium,chromium, and barium can be determined by X-ray fluorescence.

The second step of identification and characterization involves runningan X-ray diffraction scan on the catalyst. The X-ray diffraction scanwill show a pattern of peaks, which peaks have positions and intensitiesdistinctive of the crystalline phases which are present. The X-raydiffraction peak positions and intensities of the catalyst can becompared to peak positions and intensities of known crystalline phasesthat are published in the ASTM Powder Diffraction File, for example, orthat are experimentally obtained. For example, a catalyst comprised ofiron oxide merely impregnated on aluminum oxide will have an X-raydiffraction pattern of peak positions showing the distinct peakpositions and intensities of iron oxide and aluminum oxide crystallinephases.

In contrast, the X-ray diffraction pattern of a solid solution catalystcontaining iron shows the positions of the X-ray diffraction peaks inthe solid solution catalyst to be shifted from the peak positions in theX-ray diffraction pattern of the host lattice. The shift in peakpositions may be accompanied by changes in the relative intensities ofthe peaks, but the intensity changes are generally small.

The shift in X-ray diffraction peak positions when solid solutions areformed results from the expansion or contraction of the dimensions ofthe unit cell of the crystalline phase of the host lattice. Thedimensions of the unit cell of the host lattice are changed due to thesubstitution of iron cations for cations of the host lattice. If thecation is larger than the cation it displaces, the unit cell dimensionswill increase in size to accommodate the larger cation. The amount ofexpansion or contraction, if the iron cation is smaller than the hostlattice cation it displaces, of the unit cell dimensions can bedetermined by calculating the lattice parameters of the unit cell of thesolid solution phase and comparing these lattice parameters to thelattice parameters of the unit cell of the host. A change in latticeparameters due to iron in accordance with Vegard's law. Since a changein the lattice parameters causes a change in the X-ray diffraction peakpositions, a quick comparison of the X-ray diffraction pattern of thecatalyst and the pattern of the host lattice will show whether a solidsolution catalyst has been prepared.

Alternately, a more accurate method of confirming the preparation of asolid solution catalyst is to experimentally run X-ray diffraction scansof the prepared catalyst and of the host lattice and then calculate thelattice parameters of each. If the values obtained for the latticeparameters of the catalyst and host lattice are different, a solidsolution catalyst has been prepared. If the geometry and dimensions,i.e., lattice parameters, of the unit cell of the host lattice is nowknown, it can be determined using established methods for indexing andinterpreting X-ray diffraction patterns. The high 2θ values (where θ isthe Bragg angle) are normally used to calculate the lattice parameters.

In the case of a solid solution catalyst stabilized with lanthanumand/or a lanthanide and modified with at least two selected metals, theX-ray diffraction pattern will clearly show the presence of the solidsolution, which is the primary crystalline phase, and will additionallyshow the presence of crystalline lanthanum and/or lanthanide andselected metal compounds which are present in detectable amounts. Forexample, in the case of a solid solution catalyst of Fe₂ 0₃ in α-Al₂ 0₃stabilized with lanthanum and modified with cobalt and barium, the X-raydiffraction pattern will show the presence of the Fe₂ 0₃ in α-Al₂ 0₃solid solution crystalline phase, the crystalline compounds of lanthanumsuch as La₂ 0₃ and LaAl0₃, crystalline cobalt oxide, and crystallinebarium oxide.

In summary, the solid solution catalysts of this invention can beidentified and characterized by (1) the presence of iron, lanthanumand/or lanthanides, and the selected metals in the catalyst and (2) theX-ray diffraction pattern of the catalyst. The iron is present ascations substituted in the host lattice for cations of the host lattice.The iron content can be measured using standard analysis techniques. TheX-ray diffraction pattern of the solid solution catalyst will exhibitpeak positions characteristic of the host lattice but shifted due to thepresence of the iron cations in the host lattice. Lattice parameterscalculated for the host lattice and the solid solution catalyst willdiffer. The X-ray diffraction pattern of the solid solution catalysts ofthis invention will exhibit extraneous peaks in the pattern due toformation of crystalline compounds other than the solid solutioncatalyst itself, such as lanthanum oxide or lanthanide oxides, andselected metal oxides.

The solid solution catalysts used in the examples were prepared by firstimpregnating a host lattice precursor with an iron salt, a lanthanumsalt and selected metal salts or precursors that yield the oxides uponheating, then heating the impregnated host lattice precursor to about550° C. followed by heating to 1200° C. or more. The catalyst preparedis a solid solution catalyst containing iron, stabilized with lanthanumand/or lanthanides and modified with the selected metals. The catalysthas a distinctive X-ray diffraction pattern.

The solid solution catalyst can also be prepared in other ways. Anothermethod is to physically admix iron oxide, lanthanum or a lanthanideoxide, the selected metal oxides, and the host lattice material and heatthe mix to allow dissolution and substitution of the iron ions for thoseof the host lattice, and formation of the stabilized and modifiedcatalyst. Heating conditions vary due to the nature of the host latticeemployed but typically are above about 1100° C.

A third method of preparation is to use the so-called sol-gel processwherein an iron salt, lanthanum and/or lanthanide salt, selected metalsalts and a salt precursor of the host lattice are mixed together assolutions and a base is added to coprecipitate out a mixture of thecorresponding hydrated oxides. The mix is then heated to above about1100° C. to effect dissolution and substitution of the iron ions foraluminum ions.

A fourth method involves the dissolution of selected metal salts in asolvent such as water or ethanol and the use of the solution toimpregnate a preformed solid solution catalyst already stabilized withlanthanum and/or lanthanides. The mix is then dried and heated to causethe metal salts to decompose upon heating to yield the oxides.

In all of these methods, a metal oxide precursor can be used in place ofthe metal oxide per se. The precursor, which is typically a salt of themetal, decomposes on heating to yield the oxide form of the metal.Examples of iron oxide precursors are iron chloride, iron sulfate, ironformate, iron oxalate, iron citrate, iron nitrate, and the like.Precursors of the oxides of lanthanum or lanthanides and of the selectedmetals can also be employed. Examples of lanthanum oxide precursors arelanthanum nitrate, lanthanum chloride, lanthanum sulfate, lanthanumoxalate, and the like. Examples of selected metal oxide precursors arechromium acetylacetonate, chromium nitrate, chromium chloride, manganesechloride, manganese oxalate, manganese nitrate, cobalt chloride, cobaltnitrate, cobalt oxalate, barium nitrate, and barium chloride, and bariumcarbonate, magnesium chloride and magnesium nitrate.

The solid solution catalysts of this invention can be used in theprocess in the form of a fixed bed, a fluidized bed, on a fixed support,on a fluidized support, or in a number of ways well known to the art.Although in the examples the process used is a fluidized bed process, itis understood that other well known techniques can be employed. Thefollowing Examples are given to further illustrate the invention.

EXAMPLES

Solid solution catalysts were used to react ethane, oxygen and hydrogenchloride to ethylene, hydrogen chloride, vinyl chloride and steam. Thereactions were conducted in a fluid bed reactor wherein the ethane,oxygen or oxygen used in the form of air, and anhydrous hydrogenchloride were premixed at a set molar ratio of reactants and the mixturefed into a heated reactor near the bottom. The catalyst used was in theform of particles of a size passing between 80 mesh and 325 meshscreens. Contact times in the reaction were from about 4 seconds toabout 10 seconds. Products were withdrawn from the top of the reactor asgases, scrubbed with water and analyzed using a gas chromatograph. Theprocess was run as a continuous process for times of 1 hour up to 300hours or more per run.

The following examples detail experiments conducted using various moleratios of reactants, various temperatures and times of reaction, anddifferent solid solution catalysts.

EXAMPLE 1

This example demonstrates a solid solution catalyst containing theselected metals of chromium, cobalt, manganese and barium on anattrition resistant support.

A mixture of La(NO₃)₃ ·6H₂ 0(34.37 gr), Fe(NO₃)₃ ·9H₂ 0(31.9 gr),Cr(NO₃)₃ ·9H₂ 0 (7.28 gr), Co(NO₃)₂ ·6H₂ 0(5.81 g), Mn(NO₃)·6H₂ 0(5.51gr), and Ba(NO₃)₂ (7.50 qr) dissolved in distilled water was slowlyadded to 297.4 gr of particulate attrition resistant gamma Al₂ 0₃catalyst support with stirring to insure homogeneous mixing of solutionwith the catalyst support. The catalyst then was dried on a steam bathand then air dried overnight at 80° C. The dried catalyst was thencalcined at 550° C. for 16 hours and then calcined at 1250° C. for 16hours. The resulting catalyst was sieved to remove fines and used as is.

EXAMPLE 2

This example demonstrates the use of various solid solutions on anattrition resistant support catalyst of this invention as shown in TableA below in a reactor to promote the reaction of ethane, hydrogenchloride and oxygen, in the form of air, to ethylene, hydrogen chloride,vinyl chloride and steam. The reaction temperature was 550° C., contacttime with fluidized catalyst was 12 seconds, and volume ratio of thereactants, i.e., ethane, hydrogen chloride and oxygen was respectively1/1.75/0.7. The gaseous product Stream B was analyzed for the presenceof vinyl chloride (VCM) and the following results were obtained:

                  TABLE A                                                         ______________________________________                                        % La  % Fe    % Cr     % Co  % Mn   % Ba  % VCM                               ______________________________________                                        --    2.0     --       --    --     --    7.1                                 4.0   2.0     0.5      --    --     --    6.6                                 4.0   2.0     --       0.5   --     --    5.7                                 4.0   2.0     --       --    --     2.9   4.6                                 4.0   2.0     --       0.5   --     2.9   4.5                                 4.0   2.0     --       --    0.5    --    5.5                                 4.0   2.0     0.5      0.5   --     1.5   4.4                                 4.0   2.0     0.5      0.5   --     1.5   4.4                                 4.0   2.0     --       0.5   --     1.5   5.1                                 4.0   2.0     0.5      0.5   1.0    1.5   4.3                                 4.0   2.0     0.5      0.5   2.0    1.5   3.7                                 4.0   2.0     --       1.0   --     1.5   5.0                                 4.0   2.0     --       1.0   --     2.9   4.6                                 4.0   2.0     --       --    2.0    1.5   5.7                                 7.0   2.0     --       1.0   2.0    1.5   4.2                                 4.0   2.0     --       0.5   1.0    1.5   4.3                                 4.0   2.0     1.0      1.0   2.0    1.5   3.9                                 7.0   3.0     --       1.0   2.0    --    4.5                                 7.0   3.0     --       1.0    .5    1.5   4.5                                 ______________________________________                                    

The above results indicate that vinyl chloride monomer in Stream B canbe reduced substantially by the use of the solid solution catalyst ofthis invention. The presence of barium in the catalyst is shown above toreduce the formation of vinyl chloride.

In the above table, percent of the metal refers to weight percent ofthat particular metal in the solid solution catalyst and percent ofvinyl chloride monomer (VCM) refers to the number of moles of vinylchloride formed in the reaction for every 100 moles of ethane fed to thereactor. As earlier described, the metals are in the form of oxides. Forinstance, 2.0% Fe given in the above table, means 2.0% by weight offerric oxide (Fe₂ O₃) and 1.0% Mn is 1.0% by weight of manganese oxide.

I claim:
 1. A solid solution catalyst comprising α-Al₂ 0₃ catalyst support particles with iron cations substituted for aluminum cations in the host lattice of α-Al₂ 0₃ catalyst support having an iron content of 0.1 to 20% by weight expressed as the oxide stabilized with a total lanthanide content of 0.1 to 20% by weight expressed as the oxide and modified with at least two metal cations selected from the group consisting of barium, cobalt, chromium, magnesium and manganese, wherein barium is one of said metal cations and wherein said metal cations are present in amounts of 0.05 to 10% of each metal by weight expressed as the oxide; wherein said lanthanide content expressed as the oxide is selected from oxides of the elements 57 to 71 of the Periodic Table, and mixtures thereof; said solid solution catalyst having X-ray diffraction pattern having peak positions different than that of the host lattice.
 2. A solid solution catalyst of claim 1 wherein the iron content of the catalyst is 0.5 to 10% by weight, expressed as the oxide, stabilized with 0.5 to 10% by weight, expressed as the oxide, of lanthanum.
 3. A solid solution catalyst of claim 2 modified with 0.1 to 3% of each by weight of cobalt oxide and barium oxide.
 4. A solid solution catalyst of claim 2 comprising iron cations in said α-Al₂ 0₃ host lattice stabilized with lanthanum oxide and modified with 0.1 to 3% of each by weight of chromium oxide, cobalt oxide, and barium oxide.
 5. A solid solution catalyst of claim 2 comprising iron cations in said α-Al₂ 0₃ host lattice stabilized with lanthanum oxide and modified with 0.1 to 3% of each by weight of manganese oxide and barium oxide.
 6. A solid solution catalyst of claim 2 comprising iron in said αAl₂ 0₃ host lattice stabilized with lanthanum oxide and modified with 0.1 to 3% of each by weight of chromium oxide, cobalt oxide, manganese oxide, and barium oxide.
 7. A solid solution catalyst of claim 2 comprising iron in said αAl₂ 0₃ host lattice stabilized with lanthanum oxide and modified with 0.1 to 3% of each by weight of cobalt oxide and manganese oxide.
 8. A solid solution catalyst comprising iron cations substituted for aluminum cations in a host lattice of αAl₂ 0₃ having iron content of 0.5 to 10% by weight expressed as the oxide stabilized with lanthanum oxide in amount of 0.5 to 10% by weight and modified with at least two metal cations selected from the metals consisting of chromium, cobalt, manganese, magnesium and barium in amount of 0.1 to 3% by weight of each metal expressed as the oxide, wherein barium is one of said metal cations and said catalyst having X-ray diffraction pattern having peak positions different than that of the host lattice.
 9. A solid solution catalyst of claim 8 wherein amount of each said metal expressed as the oxide is 0.2 to 2% by weight.
 10. A solid solution catalyst of claim 1 wherein said αAl₂ 0₃ catalyst support particles are substantially devoid of crystalline grain boundaries, cracks and fractures and having low attrition number, as determined by the roller attrition test.
 11. A solid solution catalyst of claim 10 which is fluidizable, which is in the form of spheroidal particles, which has attrition number not exceeding 30, and which is thermally stable up to about 1000° C.
 12. A solid solution catalyst of claim 11 containing at least three metal cations and one of said metal cations is barium.
 13. A solid solution catalyst of claim 12 disposed on attrition resistant particulate αAl₂ 0₃ catalyst support passing between 80 mesh and 325 mesh screens being substantially devoid of crystalline grain boundaries, cracks and fractures with attrition number not exceeding 5 and consisting of the following components in the indicated weight amounts:(1) 4% La₂ % Fe₂ 0₃, 0.5% Cr₂ 0₃, 0.5% CoO, 1.5% BaO; (2) 4% La₂ % Fe₂ 0₃, 0.5% Cr₂ 0₃, 0.5% CoO, 1.5% Ba0,1.0% MnO; (3) 4% La₂ % Fe₂ 0₃, 0.5% Cr₂ 0₃, 0.5% CoO, 1.5% Ba0, 2.0% MnO. (4) 4% La₂ % Fe₂ 0₃, 0.5% CoO, 1% MnO, 1.5% BaO.
 14. A solid solution catalyst of claim 10 wherein the iron catalyst is to 0.5to 10% by weight, expressed as the oxide, stabilized with 0.5% to 10% by weight, expressed as the oxide, of lanthanum.
 15. A solid solution catalyst of claim 10 modified with 0.1 to 3% of each by weight of cobalt oxide and barium oxide.
 16. A solid solution catalyst of claim 10 comprising iron cations in said α-Al₂ 0₃ host lattice stabilized with lanthanum oxide and modified with 0.1 to 3% of each by weight of chromium oxide, cobalt oxide, and barium oxide.
 17. A solid solution catalyst of claim 10 comprising iron cations in said α-Al₂ 0₃ host lattice stabilized with lanthanum oxide and modified with 0.1 to 3% of each by weight of manganese oxide and barium oxide.
 18. A solid solution catalyst of claim 10 comprising iron in said α-Al₂ 0₃ host lattice stabilized with lanthanum oxide and modified with 0.1 to 3% of each by weight of chromium oxide, cobalt oxide, manganese oxide, and barium oxide.
 19. A solid solution catalyst of claim 10 comprising iron in said α-Al₂ 0₃ host lattice stabilized with lanthanum oxide and modified with 0.1 to 3% of each by weight of cobalt oxide, manganese oxide and barium oxide.
 20. A solid solution catalyst of claim 10 wherein the amount of each said metal expressed as the oxide is 0.2 to 2% by weight. 